What is the relationship of pKa to acid dissociation constant (Ka)?

The correct relationship between pKa and the acid dissociation constant (Ka) is expressed by the equation pKa = -log(Ka). This equation highlights how pKa is a logarithmic transformation of the acid dissociation constant, which quantifies the strength of an acid.

The acid dissociation constant (Ka) measures the extent to which an acid dissociates into its conjugate base and protons in solution. A larger Ka value indicates a stronger acid, meaning it dissociates more completely in solution. The pKa, on the other hand, is a more convenient way to express this value because it transforms the nonlinear scale of Ka into a more manageable format.

Since pKa is defined as the negative logarithm of Ka, a smaller pKa indicates a stronger acid (due to the fact that a larger Ka value yields a smaller pKa). This relationship is valuable in biochemistry, as it allows scientists to compare the strengths of different acids and bases in a more intuitive way. Understanding this relationship is crucial for analyzing acid-base equilibria in biochemical systems.